Restore Email Messages

I have a new Apple Pro, and I wanted to save an pdf attachment that a friend sent.  I thought that I was just saving that one attachment, so I hit the download icon at the top of the Preview box.  That saved over 100 messages from my Inbox to my Documents in Pages.  I am unable to open them or put them back.  Apple Support said they can't help me to drag and drop the messages back to email, because I access my ATT/Yahoo by going to Google first.  The data in this new Apple was transferred from my old Dell via a thumb drive and was stored in Google there.  I hope you can help.